Abstracts

Rationale: Traumatic brain injury (TBI) triggers various inflammatory mechanisms, including complement system activation, blood-brain barrier damage, platelet recruitment and activation, and peripheral immune cell infiltration. Although the precise interplay between inflammatory and neuronal mechanisms is still not fully elucidated, the evidence is mounting that inflammatory mediators play an important role in brain damage and epileptogenesis. C1-INH is a member of the serpin family of protease inhibitors, which inactivates proteases involved in activating the complement system, the contact-kinin system, and the fibrinolytic/coagulation system. C1-INH also suppress leukocyte transmigration across the endothelium. The present study evaluated the effects of C1-INH, an FDA-approved drug, on neurobehavioural outcomes, the risk of developing epilepsy and its severity.

Methods: Adult CD1 mice were subjected to controlled cortical impact injury. One hour after brain injury, mice were randomly allocated to receive a single intravenous injection of human plasma-derived C1-INH (15.0 IU Berinert^®; CSL Behring) or vehicle solution. The effects of C1-INH treatment on inflammatory responses and brain damage after TBI were examined using Cytometric Bead Array, Fluoro-Jade C staining, and Nissl staining. Neurobehavioral outcomes after TBI were assessed with neurological severity scores, the rotarod, open field, and active place avoidance tests. Epileptogenesis was examined with video-electroencephalographic monitoring in the 15th and 16th week after TBI.

Results: C1-INH decreased TNFα expression and reduced neuronal degeneration 2 days after TBI. C1-INH reduced neurological severity scores 4 hours after TBI, indicating that it improved acute neurological function (Figure 1). C1-INH did not affect motor function assessed by the rotarod test and spatial learning ability examined by active place avoidance; however, C1-INH increased locomotor activity levels and reduced anxiety-related behaviour assessed by the open field test. Spontaneous seizures were observed in a higher proportion of vehicle-treated mice compared to C1-INH-treated mice and the average seizure frequency was higher in vehicle-treated animals compared to C1-INH-treated animals but the differences were not statistically significant. The proportion of days of video-EEG monitoring in which seizures occurred was significantly lower in C1-INH-treated animals than in vehicle-treated animals. Collectively, these results suggest that C1-INH has a disease-modifying effect on epileptogenesis. At 16 weeks after TBI, C1-INH significantly reduced the percentage area of lesion in the hemisphere ipsilateral to the impact site, assessed using Nissl staining (Figure 2).

Conclusions: This study confirmed the neuroprotective and anti-inflammatory effects of C1-INH. C1-INH treatment improved neurobehavioral outcomes, and exhibited a disease-modifying effect on epileptogenesis after TBI. The safety profile of C1-INH from extensive clinical experience supports the possibility of repurposing C1-INH to combat severe TBI.

Funding: This research was funded by the Department of Defense office of the Congressionally Directed Medical Research Programs (W81XWH-17-1-0670).